Biochemistry MCQ Pdf: 

1. The average nitrogen content of various proteins is about_______

A．0.6% 

B. 6% 

C. 16% 

D．26% 

E．36%

Answer: C

2. The amino acids that makeup proteins are______

A．20 kinds of 

B．300 kinds 

C．12 kinds 

D．16 kinds of 

E．18 types

Answer: A

3. The protein content of the human body is approximately

A．30,000 kinds of 

B．100,000 kinds of 

C．1 million species 

D．1 billion species 

E. 10 billion species

Answer: B

4. Amino acids without asymmetric carbon atoms are

A．proline 

B. Glycine 

C. Cysteine ​​

D. Serine 

E．Methionine

Answer: B

5. Amino acids that form disulfide bonds in proteins are

A．Glycine 

B. Serine 

C. Cysteine ​​

D. Histidine 

E．Lysine

Answer: C

6. The amino acids that makeup protein molecules are

A．L-β-amino acid 

B. D-β-amino acid 

C. L-α-amino acid

D．D-α-amino acid 

E. L, D-α-amino acid

Answer: C

7. Which of the following is a basic amino acid

A．glutamic acid 

B. Serine 

C. Tyrosine

D．Lysine 

E．threonine

Answer: D

8. Amino acids with two carboxyl groups are

A．Serine 

B. Lysine 

C．Tyrosine

D．Threonine 

E. glutamic acid

Answer: E

9. What makes albumin (isoelectric point 4.7) positively charged in the following pH solutions is

A．PH4.0

B．PH5.0 

C．PH6.0 

D．PH7.0 

E．PH8.0

Answer: A

10. Most of the pI of plasma proteins are pH 5-6, and their main form in the blood is

A．Zwitterionic 

B. non-polar molecules 

C. Positively charged 

D. Negatively charged 

E. Hydrophobic molecule

Answer: D

11. Which statement about glutathione is true

A．As an active polypeptide 

B. The molecule contains cystine 

C. The leading functional group is hydroxyl

D．An important reducing agent in the body 

E. important oxidant in the body

Answer: D

12. The composition of the main chain backbone in the polypeptide chain is

A．－NCCNCCNCCNCC－ 

B．－CONHCONHCONH－ 

C．-CHNOCHNOCHNO-

D．-CNOHCNOHCONH- 

E. -CNHOCNHOCNHO-

Answer: A

13. Which of the following concepts has nothing to do with protein secondary structure

A．Irregular curl 

B. Subunit 

C. β-rotation angle 

D. β-sheet 

E. α-helix

Answer: B

14. Protein secondary structure does not include

A．α-helix 

B. α-double helix 

C. β-rotation angle 

D. β-sheet 

E. random curl

Answer: B

15. Both α-helices and β-sheets in protein molecules belong to

A．Primary structure 

B. Secondary structure

C. Tertiary structure

D. Four-level structure 

E. domain structure

Answer: B

16. Chemical bonds that do not directly participate in maintaining the secondary structure of proteins are

A．Hydrophobic bond 

B. hydrogen bond 

C. salt bond 

D. Disulfide bond 

E. peptide bond

Answer: E

17. Chemical bonds that can be broken when proteins are denatured do not include

A．Hydrophobic bond 

B. hydrogen bond 

C. salt bond 

D. Disulfide bond 

E. peptide bond

Answer: E

18. protein denaturation due to

A．A change in the primary structure of the protein 

B. Depolymerization of protein groups 

C. Disruption of spatial protein conformation

D．The loss of prosthetic group 

E. protein hydrolysis

Answer: C

19. The structure unchanged when the protein is denatured is

A．Primary structure 

B. Secondary structure

C. Tertiary structure

D. Four-level structure 

E. domain

Answer: A

20. The main characteristic of denatured protein is

A．Not easily hydrolyzed by proteases 

B. Decreased molecular weight 

C. increased solubility

D．Loss of biological activity 

E. covalent bond is broken

Answer: D

21. Which of the following reagents can open disulfide bonds in proteins

A．Cyanogen bromide 

B. 2,4-Dinitrobenzene 

C. β-mercaptoethanol 

D. Iodoethanol 

E. trichloroacetic acid

Answer: C

22. The main component in the protein molecule that causes the absorption of 280nm wavelength ultraviolet light is

A．The carboxyl group of glutamic acid 

B. The phenyl ring of phenylalanine 

C. indole ring of tryptophan

D．Peptide bond

E. SH group of cysteine

Answer: C

23. The main form of mixed amino acids in solution under neutral conditions is

A．Has a unit-positive charge 

B. Has a unit negative charge 

C. amphoteric ion 

D. Nonpolar molecules

E. Hydrophobic molecule

Answer: B

24. The directionality of the peptide chain of a protein is

A．From N-terminal to C-terminal 

B. From 5′ to 3′ 

C. From C-terminal to N-terminal

D．From 3′ end to 5′ end 

E. none of the above

Answer: A

25． Molecules that cause abnormalities after gene mutations in “molecular diseases” are

A．protein 

B. Nucleic acid

C. sugar 

D. Lipids

E. vitamins

Answer: A

26. In 1926, JB Sumner of the United States first obtained the crystallization of enzymes from sword beans and confirmed that enzymes are proteins. 

A: Urease 

B: Pepsin 

C: Trypsin 

D: Chymotrypsin 

Answer: A

27. In 1955, British biochemist Sanger determined the determination structure of the primary system and won the 1958 Nobel Prize in Chemistry. 

A: Bovine insulin 

B: Urease 

C: Ribozyme 

D: Chymotrypsin 

Answer: A

28. Which of the following sugars has no reducing properties

A: Maltose 

B: Sucrose 

C: Glucose 

D: Fructose 

Answer: D

29. The most abundant lipid in biological membranes is

A: Phospholipid 

B: Cholesterol 

C: Glycolipid 

D: Triacylglycerol 

Answer: A

30. What is the molecular composition of sphingolipids 

A: One molecule of fatty acid, one molecule of sphingosine or its derivatives, one molecule of polar alcohol 

B: one molecule of fatty acid, one molecule of glycerin, one molecule of phosphoric acid, and choline 

C: three molecules of fatty acid, one molecule of glycerin 

D: two molecules of fatty acid, One molecule of glycerin, and one molecule of sugar 

Answer: A